Question

A plane flies a distance d between two cities during 2 hours with an average speed of 800 km/h. A second plane covers the same distance d with an average speed of 400 km/h. The time of flight taken by the second plane to cover the distance d is equal to:

Answer 1

Answer: The time for the second flight is 4h

Answer 2

Given

Plane A

d = distance

t = 2h

v_a = 800 km/h

Plane B

d = distance

v_b = 400 km/h

Procedure

The planes cover the same distance but at different speeds so we can match the equations for distance.

`\begin{gathered} d_a=d_b \\ v_at_a=v_bt_b \\ t_b=(v_at_a)/(v_b) \\ t_b=(800km/h*2h)/(400km/h) \\ t_b=4h \end{gathered}`

The time for the second flight is 4h